The subject matter disclosed herein relates to a steam seal system for a steam turbine configuration. Specifically, the subject matter disclosed herein relates to a single header steam seal system for a steam turbine configuration.
Steam seal systems and end packings are conventionally used in turbine operations (e.g., steam turbine operations) to seal portions of a shaft near the interface between that shaft and the turbine's casing. The end packings are usually divided into two groups: pressure packings and vacuum packings. Without the steam seal system, the pressure packings would leak steam outwardly from inside the turbine casing (e.g., into the turbine room), while the vacuum packings would leak air from the atmosphere into the turbine casing. The conventional steam seal system attempts to solve these problems by utilizing the steam leaking from the pressure packings to seal the vacuum packings.
The conventional sealing steam is maintained at a constant pressure (slightly higher than atmospheric, e.g., 4 pounds per square inch gauge (psig)) by a steam seal regulator in a steam seal header (SSH). In order to prevent the pressure packings from allowing leakage of steam into the turbine room (from within the turbine casing), a steam packing exhauster (SPE) is used to extract steam from an outermost ring at each packing, creating a slight (e.g., −0.2 psig) vacuum.
Conventionally, the SSH and SPE pressures remain constant throughout all load conditions of the turbine system, including, e.g., low loads, transient loads, etc. In times of low load, where the extracted steam mass flow may be insufficient to form an effective seal, additional steam may be supplied from an external source (e.g., an auxiliary boiler).
Unfortunately, the conventional steam sealing system requires that end packings (e.g., those endpackings at a high pressure (HP) or intermediate pressure (IP) turbine) are designed for sealing purposes, and not performance. Additionally, the conventional steam sealing system uses high-pressure and intermediate-pressure steam from the HP and IP turbines, respectively, to provide sealing steam for the LP turbine. This can require that the higher-pressure (and correspondingly, high temperature) steam be cooled before it is introduced to the LP end packings. Further, the use of this extraction steam from the HP and IP turbines for sealing the LP turbine end packings causes a loss of efficiency, as the higher-energy steam from those HP and IP turbines could be more effectively used in driving a portion of the turbine system.